I agree that it is hard to judge keepers in poor sides.It is either this or you will have to start believing in coincidences that defy logic. 2 of the most praised GK's of last season, Ramsdale and Johnstone...both in relegated teams. Pickford get a big move to Everton largely for his performances in a relegated Sunderland. He has failed to live up to those highs ever since.
Simon Mignolet got his move to Liverpool by looking great in a Sunderland side who were flirting with relegation most of the time.
Even our own Leno's best season was with Emery when we were conceding 30 shots a game.
One thing that stuck with me is I remember Peter Schmeichel saying it was much harder being a goalkeeper for Man Utd than a poorer side. I guess it was even more the case in those days with less playing out from the back, he said that he could barely touch the ball for an hour and then suddenly he had to go into action from cold.
Keeping at the top level of concentration when you are pretty much a bystander for long periods must be so difficult. I appreciate the skill and mental toughness because I played international level pool for a decade. The hardest part of the game was when the other guy was getting all the table time and then suddenly you get your chance when you are cold. It was always easy to play well when it was the other way round and I was the guy who was warm and flowing.